1. Field of the Invention
The present invention pertains to an apparatus and method for x-ray imaging coilable tubing used for injection into subterranean wells for inspecting the integrity of the tubing.
2. Background
An increasingly popular method of performing well operations comprises extending continuous lengths of relatively thinwalled steel tubing into the wellbore for the injection of fluids, well cleanout operations and the insertion and withdrawal of certain wellbore tools. An advantage of utilizing such tubing is that the tubing may be stored on a reel in a continuous length similar to a cable and the tubing is, of course, capable of conducting fluids into and out of the wellbore and serving as a sheath or shield for electrical conductors.
However, since the tubing undergoes plastic deformation with each dereeling, injection, withdrawal and re-reeling operation, it is important to monitor the onset of fatigue cracking or the detection of any other defect in the structure of the tubing. In this respect, prior art efforts to inspect coilable tubing has required complete dereeling of the tubing from its storage spool while passing the tubing through conventional inspection equipment. This process is time consuming and since the tubing must be re-reeled and then dereeled again during use, a fatigue crack may develop after the inspection process, but at an early time during subsequent use. In this regard, it has been considered highly desirable to be able to inspect coiled tubing before injection into the wellbore, during each injection operation or during withdrawal of the tubing after each use thereof. In this way, the risk of catastrophic failure of the tubing while it is in the wellbore is minimized and early detection of fatigue cracks or fissures which may result in tube failure or at least provide a fluid leakage flow path which could seriously damage or impair well operations is provided.
The present invention is directed to providing a method and apparatus for substantially continuous inspection of coiled tubing at the wellsite both before and after use of the tubing for injection into a wellbore.